#include <bits/stdc++.h>

using namespace std;

ifstream fin("lupu.in");
ofstream fout("lupu.out");
priority_queue<int> maHeap;
pair<int, int> o[100002];
int n, x, l, i, ma;
long long rasp;

int main() {
    fin >> n >> x >> l;
    for(i = 1; i <= n; i++) {
        fin >> o[i].first >> o[i].second;
    }

    sort(o + 1, o + n + 1);

    int idxOaie = 1;
    for(i = 0; i <= x / l; i++) {
        int ma = i * l;

        while(idxOaie <= n && o[idxOaie].first <= ma) {
            maHeap.push(o[idxOaie].second);
            idxOaie++;
        }

        if(!maHeap.empty()){
            rasp += maHeap.top();
            maHeap.pop();
        }
    }

    fout << rasp;

    return 0;
}